Electron discharge tube



April 29, 1947. I J. FOSTER 2,419,544

ELECTRON iJISCHARGE TUBE Filed June 2, 1942 WW By 1 mm ATTORNEY Patented Apr. 29, 1947 UNITED STATES ATENT OFFICE ELECTRON DISCHARGE TUBE Application June 2, 1942, Serial No. 445,509. In Great Britain June 13, 1941 4 Claims.

This invention relates to electron discharge tubes and has for its main object to provide an improved construction of tube for ultra high frequencies.

The tube according to this invention comprises two envelope portions separated by a metallic disc which extends outside said envelope portions with a cathode and grid mounted in one envelope portion and an anode in the other, the metallic disc being provided with an aperture and electrically connected with the grid which is adjacent said aperture, whereby the grid is common to both envelope portions and the input and output sides of the tube are efiectively screened from one another by the metallic disc.

The electrical connection between the metallic disc and the grid is preferably effected by contact springs associated with the grid and arranged to make contact with the metallic disc when the tube is assembled.

The above and other features of the invention will be hereinafter described with reference to the accompanying drawings, in which:

Figure 1 is a sectional view of a tube constructed according to the invention,

Figure 2 is an exploded view showing the variious tube elements, and

Figure 3 is a detail view on an enlarged scale showing the engagement of the mica grid support in the aperture of the grid disc.

Fig. 4 is an enlarged detail of the sectional view shown in Fig. 1 showing the cathode, grid and grid supports.

In these drawings, l and 2 represent the cylindrical glass envelope portions and 3 the copper grid disc which is sealed between them as by heating the copper disc. The grid disc 3 has an annular dished formation as shown and projects well beyond the glass envelope portion to form an effective screen between the two halves of the tube and also to provide a mounting device for supporting the tube. If desired, the projecting flange portion may be provided with holes 15 to accommodate supporting bolts. The center of the disc is provided with an aperture t to accommodate the grid 5 which, together with the cathode, is mounted on the pinch 6 in the envelope portion The grid is wound around two spaced grid supporting rods indicated at l and carried by mica end plates 8. The grid wires are secured to the supporting rods 1 and in order to reduce the capacity between the grid 5 and cathode 9 the lower turns of the grid are all or mostly all cut away to leave a single layer grid structure as shown in Fig. 4.

The grid supports are provided with contact springs l0 adjacent the mica supports 8, and these mica supports are arranged to engage slots If on the edges of the aperture 4 of the copper disc 3, as clearly shown in Figure 3. In this way, when the copper disc 3 is assembled on the envelope portion containing the grid cathode structure, the mica supports 8 engage the slots H to locate the grid within the aperture 4, and at the same time the contact springs ID associated with the grid establish contact with the disc 3 so that the disc is effectively connected electrically to the grid.

The envelope portion 2 carries the anode l2 which is a copper thimble-shaped element sealed at 53 into the re-entrant portion of the envelope so that the anode is accessible for direct connection as by a connector inserted within the hollow thimble. The anode l2 may be provided with a rectangular end piece I4 to conform to the shape of the grid aperture in the disc 3.

This construction allows a very close spacing of the tube elements, and provides a simple form of manufacture, as a conventional type of grid cathode structure is employed which is dropsealed into the envelope, and the connection with the grid is made automatically on assembly of the grid disc, the anode being sealed into the opposite end of the bulb and automatically located by sealing of the bulb to the disc.

The tube is particularly applicable for use in an inverted or earthed-grid circuit, and tests so far made have shown that high frequency tubes constructed in accordance with this invention may be produced to have a very high gain compared with other known forms of tube. In applying the tube to concentric conductor transmission lines the central conductor may be connected directly to the thimble anode and the grid disc may be connected directly or by capacitative coupling with the outer conductor.

What is claimed is:

1. An electron discharge tube comprising a cathode, a grid, an anode, two envelope portions separated by a metallic disc which extends outside said envelope portions, said cathode and grid comprising a unit, means mounted in one envelope portion supporting said unit, means mounted in the other envelope portion supporting said anode, said metallic disc being provided with an aperture adjacent said grid, and a plurality of contact springs mounted on said grid supporting means and contacting the metallic disc and forming an electrical connection between the metallic disc and the grid.

2. An electron discharge tube according to claim 1 wherein the metallic disc is provided with slits and said grid supporting means comprises projections engaging said slits whereby the accurate location of the grid and contact springs relative to the metallic disc is ensured.

3. An electron discharge tube according to claim 1 wherein the other said envelope portions includes a reentrant portion and in which said means supporting said unit comprises means mounting the grid and cathode on a pinch sealed into one end of one of the envelope portions and the anode comprises a cylindrical portion sealed into the reentrant portion of the other of said two envelope portions and a fiat end portion on said cylindrical portion, said fiat end portion comprising the active portion of said anode.

4. An electron discharge tube according to claim 1 in which said grid comprises the turns on only one side of a winding around two spaced rods.

JOHN FOSTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,091,443 Heintz Aug. 31, 1937 1,850,104 Hansell Mar. 22, 1932 2,151,781 Lindenblad Mar. 28, 1939 1,947,179 Acheson Feb. 13, 1934 1,970,532 Bouwers Aug. 14, 1934 2,151,781 Lindenblad Mar. 28, 1939 1,994,760 Eitel Mar. 19, 1935 1,748,175 Holden Feb. 25, 1930 1,385,873 Hull July 26, 1921 2,280,980 Samuel Apr. 28, 1942 

